The present invention relates to flush valves that control the flow of water from toilet tanks to toilet bowls, and in particular, to flush valves with improved flow characteristics.
Systems for controlling the flush of toilet tank water to a toilet bowl are known, see e.g. U.S. Pat. Nos. 4,172,299 and 6,178,567. Such systems have a water inlet valve for the tank that is typically controlled by a float that senses tank water level. A flapper controls the flow of the tank water through an outlet at the bottom of the tank. Depressing the trip lever unseats the flapper so that water can empty from the tank into the bowl. As the tank water drains, the float drops with the water level in the tank, thereby triggering inlet water flow. The water level drops faster than the inlet water enters so that the flapper can drop down to reseal the outlet, and the water level in the tank can be re-established. As the tank refills, the float rises with the water and eventually closes the inlet valve to shut off the water supply.
The ability of the toilet, particularly low water consumption toilets, to operate efficiently during a flush cycle is largely a function of the pathway through which the water has to travel to exit the toilet. This pathway runs from the flush valve and through the vitreous path of the bowl. Various trapway configurations have been devised to optimize flow characteristics during the flush cycle.
Relatively little of the prior efforts to improve flush performance has been to address the impact of the tank flush valve. Conventional flush valves typically have a circular opening with a cylindrical passage leading down to the outlet of the tank, see e.g., U.S. Pat. No. 5,325,547. The cylindrical construction of such valves may create an air pocket in the flow pathway after a flush is initiated because the water in the tank narrows as it accelerates under gravity through the valve. Flush valves with non-cylindrical passageways have been devised. For example, U.S. Pat. No. 5,195,190 discloses a flush valve with a passageway in the form of conical section. The decreasing diameter of the passageway in such a valve helps reduce the volume of unwanted air. However, while an improvement, the frusto-conical passageway provides less than optimal flush efficiency.
Another part of the flush valve that can have low flow efficiency is the overflow. The overflow is used in the toilet to provide a drain passage for excess water in the tank that may arise if the water supply was not shut off in time, for example by failure of the inlet seal or the float tripping the inlet valve too late. The overflow connects to the outlet of the flush valve so that excess water can pass into the bowl and to the waste plumbing lines. Conventional overflow tubes are long upright cylinders with the lower end communicating with the main flow passage of the flush valve and the upper end extending slightly above the desired normal full water level in the tank, see e.g. U.S. Pat. No. 4,433,446. Such cylindrical overflow tubes suffer similar less than optimal flow characteristics as do the cylindrical flush valves.
U.S. Pat. Nos. 6,401,269 and 6,651,264 both disclose flush valve assemblies that have stout, rectangular overflow tubes with relatively large mouths at the upper ends and tapering walls. While the wide mouth and narrowing construction do affect flow efficiency relative to conventional cylindrical overflow tubes, the generally rectangular cross-section still provides less than ideal flow.
Thus, a need exists for a flush valve with improved flow characteristics.